Among the ceramic materials calcium phosphate ceramic material is a main component of bone and tooth, has superior biocompatibility, and is superior in the safety. Therefore, it is widely known as a medical material such as artificial bone, artificial dental root and the like, or biomaterials such as dental cement and the like.
Among these, the research and development are actively performed in recent years of ceramic materials suitable for an artificial bone used for repairing or healing by filling in a defect or hole made in the bone die to a disease such as bone fracture, bone tumor and the like or a treatment thereof. Although ceramic materials are already used widely in the clinical practice, current ceramic materials are defective in that the new bone formation after embedding into an affected part is limited to the surface layer of the material and the strength is not sufficient, thereby prolonging the time necessary for healing the injury.
Accordingly, the development of a ceramic implant material, which allows a biological tissue to rapidly penetrate the inside and quickly form a tissue (new bone), and has a practical strength, is desired.
As such ceramic implant material, (1) calcium phosphate sintered body wherein many pores are densely distributed three-dimensionally, and a skeleton wall compartmentalizing adjacent pores has linked sphere-like opened pores communicating with them (see patent document 1), (2) a method of forming bead-shaped porous ceramic materials having pores by connecting them with a nylon wire and the like (see patent document 2) and the like are suggested.
Moreover, it is disclosed that a sintered body having unidirectionally-oriented pores with a diameter of 10-500 μm is a ceramic material suitable as an implant material (see patent document 3).    patent document 1: JP-B-3470759    patent document 2: JP-A-2003-335574    patent document 3: JP-A-2004-275202